1. Field of the Invention
The invention relates to multiple-element clutches and, more particularly, to multiple-plate clutches employed in transmissions.
2. Description of the Prior Art
Multiple-plate clutches are commonly used in power-transmitting devices. In general, such clutches serve to selectively couple two members. This is commonly accomplished by having a plurality of plates affixed to a first member engage a plurality of plates affixed to a second member so that when all the plates are forced together in frictional engagement, the members are locked or coupled together. The multiple-plate clutch may be used to couple a rotating member to a member which it is desired to rotate. Such a clutch also may be used to connect a fixed member and a rotating member so that the rotation of the rotating member is stopped.
The chief problem with previous multiple-plate wet clutches has been their power absorption when the plates are not engaged but are proximate one another and there is rotational activity between adjacent plates. This can be of most concern when a first member coupled to a first set of clutch plates is under power while a second member coupled to a second set of clutch plates is not under power. In such a case, because of the closeness of the plates attached to each member and viscous drag occurring therebetween, the plates attached to the powered member tend to cause the plates attached to the non-powered member to rotate. Thus, the viscous drag interaction of the plates causes power losses which lead to inefficiency of the overall device in which the clutch is incorporated.
The foregoing undesirable condition may be solved by spacing the plates at a great enough distance from each other so that viscous interaction is minimized. However, this is generally not feasible because of space constraints and because of the longer times required to effect clutch engagement. In a structure according to the present invention, the clutch plates are permitted to rotate together with little or no relative motion, so that little viscous drag occurs between the plates.
Accordingly, it is an object of the invention to provide a new and improved multiple-plate clutch wherein the plates of the clutch in the disengaged mode are free to rotate at a speed in order that viscous drag losses may be eliminated or greatly reduced.